The present invention relates to forms, patterns molds, and the like for forming flowable compositions, and more particularly to the same which comprise polymer gels.
The process of forming flowable compositions into preselected shapes involves the use of patterns (usually positive shape), molds (usually negative shape), cores (including fugitive cores), plates, forms, templates, dies, components of the foregoing, and the like. The term xe2x80x9cmoldxe2x80x9d is defined and used hereinafter as an inclusive term and, unless otherwise specified, means any or all of the foregoing and any equivalents thereof.
Flowable compositions are brought into contact with a mold, take on the shape thereof, and subsequently solidified. Mold materials are generally nonporous and rigid, and are often machined into a preselected mold shape. There is a significant cost involved in preparing machined molds which could be avoided if suitable castable materials were available. Also, rigid molds are prone to problems (due to, for example, friction stress) associated with removal of formed product from the mold.
Of particular interest are molds for forming gelcasting compositions, especially for prototyping and small lot production runs. A simple and inexpensive molding system is needed for such forming tasks.
Research has shown that many castable mold materials are unsuitable for gelcasting. For example, silicone, urethane, and various waxes have disadvantageous surface reactions with gelcasting compositions which distort the formed product. Conventional plaster of paris molds are porous and draw water and other liquid solvents and/or vehicles out of the gelcasting slurry.
In order to provide comparison data, silicone elastomer and mold wax were evaluated as molds for gelcast aluminum oxide. The effect of mold release agents generally considered to be superior with respect to gelcasting aluminum oxide was shown to be of little use with silicones such as RTV (Trade name of silicones manufactured by GE Silicones, General Electric Company, Waterford, N.Y. 12188) and wax mold material such as BW2260 (available from Blended Waxes, Inc.) As shown in Table I, no material in this series of trials yielded an acceptable level of surface feature retention. As cast samples were characterized by ungelled (unpolymerized) surface layers or poor feature retention. Dried samples were characterized by surface flaking or poor surface features.
Accordingly, objects of the present invention include the provision of non-rigid molds which are inexpensively and easily fabricated, are not prone to problems due to friction stress associated with removal of formed product from the mold, and do not have surface reactions with gelcasting compositions which distort the formed product. Further and other objects of the present invention will become apparent from the description contained herein.
In accordance with one aspect of the present invention, the foregoing and other objects are achieved by a mold which includes a polymer gel body which defines a preselected shape so that a flowable composition may be formed into the preselected shape via contact with the mold.
In accordance with another aspect of the present invention, a method of forming a flowable composition into a preselected shape which includes the steps of
Step 1. forming a polymer gel into a mold which defines a preselected shape;
Step 2. contacting a flowable composition with the mold to form the flowable composition into the preselected shape; and,
Step 3. solidifying the flowable composition to produce a formed article.